Ikora Rey: When the Red Legion attacked, it almost cost us everything. It took a miracle to save us… the awakening of the Traveller. This is our new beginning. The maps are blank. The rules are gone. All we know is we must become more than what we were. This small corner of the cosmos is the only place that is forever ours. And the universe watches us with envious eyes. We've proven we can fight threats from beyond the stars. But now there are things stirring beneath our feet… provoked by the Traveler's Light. Our war… is just beginning.

Infinite Forest

A fireteam prepares an assault on the Vault of Glass, but seems to be frozen in time as Osiris appears through a portal.

Sagira: You know, I can't help but notice that even with all of reality to explore… you keep picking the places where they shoot at us.

Osiris: We can't stay here… If the Vex succeed, it's the end of everything.

A Vex projection exposes Sagira

Osiris: Sagira, it can see your Light. You have to go.

Sagira: Nope, not leaving you. Without me, there is no coming back.

Osiris: If I don't stop the Vex, there won't be anything to come back to. I'm doing this for the both of us.

Osiris opens another portal and grabs Sagira before throwing her in

Sagira: Don't you even — OSIRIS!!! ARGH

A Vex manages to hit Sagira as she flies through the portal. She lands in sand on Mercury, on the other side of the portal to the Infinite Forest.

The Tower, Earth

Ikora Rey: Guardian. Thank you for coming. There's been a development on Mercury. Strange reports from the cultists clinging to what's left of the planet. Normally, I'd ignore their conspiracy theories. But one of my Hidden brought me… this.

Ikora reveals Sagira

Ghost: A dead Ghost?

Ikora Rey: She's not dead. Her name is Sagira. I've known her a very long time… and her Guardian… Osiris.

Ghost: THE Osiris? The most powerful Guardian ever? The hero of Six Fronts? The Zavala before Zavala?

Ikora Rey: Zavala wouldn't like to hear you call him that. Most Guardian won't even speak Osiris's name. He was he only Vanguard Commander ever exiled from the City… and the man who taught me what it means to be a Warlock. We found Sagira on Mercury— and at the same time, Vex activity there surged exponentially.

Ghost: And you think Osiris might be involved?

Ikora Rey: I need to know what happened. Even if the Vanguard wants to forget him. When I lost my Light, I didn't have anything else. I was… empty. Then you came to Io, and you helped me find my way back. I need that friend again, Guardian. Go to Mercury— take Sagira with you. The Followers of Osiris, the few who remain, might know what her presence means. And for now, let's keep this between us. I'd hate to have to throw you off this wall.

Ghost: Um… That was a joke, right?

Ikora Rey: That… was a joke.

The Guardian journeys to Mercury

Ikora Rey: The Traveler transformed Mercury into a garden world. It was a paradise… until the Vex came. The Vex replaced the planet's core with their own machines. We call it the "Infinite Forest." An ever expanding labyrinth of realities. No two paths are ever the same. No one has ever escaped. It was Osiris's… obsession.

The Guardian flies down to Mercury and transmats onto the surface.

Brother Vance: Welcome to Mercury, Guardian. The signs told me you would come.

Ghost: What a coincidence. We followed the signs here, too. And by signs, I mean facts.

Brother Vance: That too is a sign! I am Brother Vance of the Followers of Osiris, keeper of the Lighthouse, and oracle of the Lost Prophecies.

The Lighthouse, Fields of Glass

Ikora Rey: There is a Vex gateway near your location. Osiris spent years studying it. He was convinced it was the door to the infinite Forest. If it is still possible to find Osiris, we need to open that door.

Brother Vance: Ikora Rey! Osiris's greatest student!

Ikora Rey: Brother Vance. Osiris's greatest… fan.

The Guardian searches for the doorway to the Infinite Forest, getting closer to The Lighthouse.

Brother Vance: I'm so pleased that Osiris has brought you to me, his most faithful servant.

Ikora Rey: Considering how you revere a man who questions everything, I am surprised how well faith serves you.

Brother Vance: The Vex are at my door. Osiris has not returned. Faith is all I have left.

The Guardian uses a Vex jump to cross a chasm, bringing the Gateway to the Infinite Forest into sight.

Ghost: The gateway to the Infinite Forest. A place from which no one has ever returned. Not even Osiris.

Agoros, Gatekeeper blocks the Guardian from reaching the gateway.

Ghost: Here it is. Well… I'm ready if you are?

The Guardian approaches the Gateway

Ghost: We can't get through. If Osiris's ghost were awake, then maybe she could help.

Brother Vance: Osiris preserve us! You have his Ghost? Sagira? Please— please— bring her to me!

Vex reinforcements arrive, including Tyranos, Gatekeeper

Ghost: Descendants… we haven't seen these Vex since the Vault of Glass.

The Guardian fights off more descendant Vex before killing Methodios, Module Proxy.

Ghost: There! Take out the module!

The Guardian shoots the module disabling the teleporter.

Ghost: Vex from different timelines are converging on Mercury. That's bad.

The Guardian uses the Vex teleporter to teleport into the Lighthouse.

Brother Vance: Thank you. I don't know what I would have done if Osiris hadn't sent you to me. In return, the Followers of Osiris can help you revive his Ghost. We have a hidden temple on Earth. Take Sagira to these coordinates. I will notify the Followers that you are coming. Now that the Lighthouse is safe, we can prepare for Osiris's return. All the lost prophecies are coming to pass. I'm finally going to meet Osiris!